Ok, I picked up a RatShack 2 wire pcb-mount electret mike today, 270-090 for $2.59. The specs that their webpage link to do not match those given on the back of the package though. Package is;

V+: nominally 4.5V, 1V < V+ < 10V
ID: 0.3mA max.
SnR: 60dB min.
Sensitivity: -64 +/-2dB
Ro: 1kohm.

Frequency response graph is identical to that which Tony scanned earlier in the thread, flat from 30Hz to about 2.5kHz, 10dB/octave rise to 5kHz, 10dB/octave rolloff from 5KHz (ie 0dB at 10kHz).

I also picked up a cable. It turns out that RatShack sell one ideally suited to this task - 1/8" mono plug to tinned wire ends, 6' long, for $3.29. (42-2434)

I'll let you know how I get on with this when I get a chance to play with it.